1. Field of the Invention
This invention pertains to optical printed symbol formats for machine readable, optical scanning systems, and more particularly to a printed symbol format having nine horizontally oriented alternate bars and spaces arranged vertically in a generally hour-glass shaped structure such that a set of such printed symbols representing a given code becomes a special font. The unique shape of the printed symbols representing a coded pattern may be readily detected, and lends itself to word or sequence identification.
2. Description of the Prior Art
The prior art in machine readable, optical scanning and recognition systems contains a wide variety of signs and symbols which are used to represent alphabetical, numeric and special function characters, usually in some coded pattern. In order to be machine readable, the printed symbols representing a given code must adhere to some rigid format, the limitations of the format being imposed by the devices being utilized to scan or read the symbols. Thus, the designer of a symbol for optical system recognition is faces with several problems. The symbol should be simple to read in the sense that a simple rather than a complex scanner can read it. The symbol should be small in physical size, to achieve a great packing density, thereby conveying a large amount of information in a small physical space. The symbol should be designed to minimize errors in its reading or interpretation.
In the present state of the art in optical symbol scanning and recognition systems, a variety of printed symbol formats are available, each having its advantages and disadvantages. One such symbol system is called Optical Character Recognition. In this system the machine-readable font is also a human readable font. Several such fonts are available and include both alphabetic and numeric characters. Among the disadvantages of the system are the high cost of readers and the low packing density of the characters, limited by the average person's ability to read. In the field of non-human readable symbols systems, various types of bar codes have become predominant. Optical bar codes print data in the form of specific patterns of bars and spaces to denote each character. Bars and spaces can be narrow or wide, and bars can be color coded. The bars are usually vertically oriented, (although one horizontally oriented system is commercially available). Optical bar codes can be alphanumeric, such as Code 39, or can be numeric only, such as the Universal Product Code. While the costs of readers for optical bar code systems are significantly lower than similar costs for optical character recognition systems, these systems presently have some disadvantages. One problem is with packing density, that is, the number of characters which can be printed per inch. Another is the ability to search and find a specific symbol within a set of characters. Another problem is the tolerances possible with the skew angle of the scanner. A fourth problem is the need for extra bits such as a clock bit.
It has become commercially desirable to provide more machine readable data per square inch than is presently possible with available encoding techniques. The optical printed symbol of the present invention presents a means by which a full alphanumeric character set can be represented by a printed symbol which can be read by a scanner either in contact with a symbol or remotely. This symbol is called an optical printed symbol because it is optically read by a scanner and because its characteristics fall between a bar code (which is referred to as a linear code) and OCR (optical character recognition) in which the optical representation and a human readable font are combined in the same image.
Accordingly, it is the object of the present invention to provide an optical printed symbol which allows the maximum packing density per symbol, while sacrificing a little in the cost of a reading device somewhat more expensive than those presently used for reading standard bar codes but having ability to search and find a symbol over a wider area. The present invention represents a novel variation in bar codes specifically designed to resolve the problems encountered with the previous symbolism.